Olfactory glomeruli are believed to have roles in odor discrimination and odor memory. Key to elucidating their roles will be an understanding of the molecular steps involved in the establishment of glomerular odor memory. Not only would this offer insights into olfactory function and pathology, but it also develops a useful model system for category memory that could be compared with other brain regions. This proposal uses honeybees, which are easily associatively trained to odors and have relatively simple brain olfactory pathways, including a glomerularized region called the antennal lobe that is strongly analogous to the vertebrate olfactory lobe. Glomeruli have a role in odor memory, and recent work has implicated nitric oxide (NO) production as a key early step in odor memory. Its synthetic enzymes are found in high concentrations in the glomeruli, and suppressing its synthesis disrupts odor memory. Since NO is believed to operate through effects on cyclic nucleotide synthesis, this proposal seeks to determine: 1. Do cyclic nucleotides change in a predictable manner in a subset of glomeruli during odor learning? Animals will be associatively-trained to different odors or sham-trained, and the distribution of cAMP and cGMP in their antennal lobe glomeruli will be examined with immunocytochemistry of quick-fixed and sectioned brains. 2. Can administration of cyclic nucleotide agonists and antagonists directly into the olfactory glomeruli affect odor learning and memory? Agonists or antagonists of either cAMP or cGMP will be microinjected into bee antennal lobes just prior to odor-association training. After training, their effects will be examined by testing the bees' odor memory.